1. Field of the Invention
The present invention relates to a sensor for blood component analysis.
2. Related Background Art
Conventionally, sensors for blood component analysis have been used for clinical test, self-measurement of blood glucose level by diabetics, etc. (see JP 2001-346781 A, for example). FIG. 10 shows an example of a sensor for measuring a blood glucose level. As shown in FIG. 10, in this sensor 1000, a working electrode 1002 and a counter electrode 1003 are formed on an insulating base material 1001, and a reagent layer is disposed on these electrodes, thereby forming an analysis portion 1004. The reagent layer contains an oxidoreductase (e.g., glucose oxidase), a mediator, and the like. A cover 1005 is disposed on the substrate 1001 so as to cover an entire area excluding one end portion (the end portion on the right in FIG. 10) with a spacer (not shown) intervening therebetween. The analysis portion 1004 communicates with a channel 1018 for leading blood to the analysis portion. The channel 1018 extends to the other end portion (the end portion on the left in FIG. 10) of the sensor, and the tip of the channel 1018 is open toward the outside of the sensor so as to serve as a blood inlet port 1019. The working electrode 1002 is connected to a lead 1022, and the counter electrode 1003 is connected to a lead 1023. These leads extend to the above-described one end portion of the sensor with the tip of each lead not being covered with the cover but being exposed.
Measurement of blood glucose level using this sensor can be carried out in the following manner, for example. First, a fingertip or the like is punctured with a dedicated lancet to cause bleeding. On the other hand, the sensor is set in a dedicated measuring device. The blood inlet port of the sensor that is set in the measuring device is brought into contact with the blood that has come out, so that the blood is led to the analysis portion in the sensor by a capillary phenomenon. In the analysis portion, glucose in the blood reacts with the oxidoreductase such as glucose oxidase contained in the reagent. Thus, when a voltage is applied between the electrodes after a lapse of a certain period, a redox current flows. The electrodes detect the current, which is then measured by the measuring device. The measuring device converts the measured value into an amount of glucose and displays the value obtained by the conversion.
In recent years, in the development of sensors for blood component analysis to be used for self-measurement, various efforts have been made to reduce the amount of blood required for the measurement, as one attempt to alleviate the burden on the subjects. However, as the amount of blood is reduced, it becomes more difficult to supply the blood to an analysis portion of a sensor, which may result in failure of measurement or measurement errors.